Bioaugmentation strategy for overcoming ammonia inhibition during biomethanation of a protein-rich substrate

Abstract

High ammonia levels inhibit anaerobic digestion (AD) process and bioaugmentation with ammonia tolerant methanogenic culture is proposed to alleviate ammonia inhibition. In the current study, hydrogenotrophic Methanoculleus bourgensis was bioaugmented in an ammonia-inhibited continuous reactor fed mainly with microalgae (a protein-rich biomass), at extreme ammonia levels (i.e. 11 g NH 4 + -N L -1 ). The results showed 28% increase in methane production immediately after bioaugmentation.Moreover, volatile fatty acids decreased rapidly from more than 5 g L -1 to around 1 g L -1 , with a fast reduction in propionate concentration. High throughput 16s rRNA gene sequencing demonstrated that the bioaugmented M. bourgensis doubled its relative abundance after bioaugmentation. "Microbiological domino effect", triggered by the bioaugmented M. bourgensis establishing a newly efficient community, was proposed as the working mechanism of the successful bioaugmentation. Additionally, a strong aceticlastic methanogenesis was found at the end of the experiment evidenced by the dominant presence of Methanosarcina soligelidi and the low abundance of syntrophic acetate oxidising bacteria at the final period. Overall, for the first time, this study proved the positive effect of bioaugmentation on ammonia inhibition alleviation of the microalgae-dominating fed reactor, paving the way of efficient utilization of other protein-rich substrates in the future.

Effect of ammonia on anaerobic digestion of municipal solid waste: Inhibitory performance, bioaugmentation and microbiome functional reconstruction

“…To pinpoint the key role of specific consortia in the AD process [17], Westerholm et al (2012) proved that the addition of SAOB cultures alone couldn't improve the performance at an ammonia load of 11 g NH4 + -N/L [22]. However, bioaugmentation with hydrogenotrophic methanogens alone could dramatically stimulate the growth of SAOB, rapidly alleviating the acetateammonia co-inhibitory effect in thermophilic and mesophilic reactors [23,24]. Despite this, the metabolic pathways and microbial interactions induced by bioaugmentation and being responsible for improving methane production remain unknown.…”

Hydrogenotrophic methanogens are the key for a successful bioaugmentation to alleviate ammonia inhibition in thermophilic anaerobic digesters

“…In recent years, bioaugmentation has been reported to alleviate ammonia inhibition in mesophilic continuously stirred tank reactor (CSTR) (Fotidis et al, 2014;Tian et al, 2019a). However, the basic bioaugmentation working mechanism and the microbiological interactions that allow a fast and successful bioaugmentation have not been clearly identified yet.…”

Modelling bioaugmentation: Engineering intervention in anaerobic digestion

“…In the simulated data, the improvement was 35 %. The increase of biogas production in R Bioaug compared to the R Control was presumably due to the "domino effect" described by Tian et al [42]: the inhibition was mainly caused by high hydrogen concentration in the liquid phase- J o u r n a l P r e -p r o o f methanogenic archaea, which accounts for the better methane productivity and microbial growth seen in Figure 1.…”